/*

 * jutils.c

 *

 * Copyright (C) 1991-1995, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This file contains tables and miscellaneous utility routines needed

 * for both compression and decompression.

 * Note we prefix all global names with "j" to minimize conflicts with

 * a surrounding application.

 */



#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"





/*

 * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element

 * of a DCT block read in natural order (left to right, top to bottom).

 */



const int jpeg_zigzag_order[DCTSIZE2] = {

   0,  1,  5,  6, 14, 15, 27, 28,

   2,  4,  7, 13, 16, 26, 29, 42,

   3,  8, 12, 17, 25, 30, 41, 43,

   9, 11, 18, 24, 31, 40, 44, 53,

  10, 19, 23, 32, 39, 45, 52, 54,

  20, 22, 33, 38, 46, 51, 55, 60,

  21, 34, 37, 47, 50, 56, 59, 61,

  35, 36, 48, 49, 57, 58, 62, 63

};



/*

 * jpeg_natural_order[i] is the natural-order position of the i'th element

 * of zigzag order.

 *

 * When reading corrupted data, the Huffman decoders could attempt

 * to reference an entry beyond the end of this array (if the decoded

 * zero run length reaches past the end of the block).  To prevent

 * wild stores without adding an inner-loop test, we put some extra

 * "63"s after the real entries.  This will cause the extra coefficient

 * to be stored in location 63 of the block, not somewhere random.

 * The worst case would be a run-length of 15, which means we need 16

 * fake entries.

 */



const int jpeg_natural_order[DCTSIZE2+16] = {

  0,  1,  8, 16,  9,  2,  3, 10,

 17, 24, 32, 25, 18, 11,  4,  5,

 12, 19, 26, 33, 40, 48, 41, 34,

 27, 20, 13,  6,  7, 14, 21, 28,

 35, 42, 49, 56, 57, 50, 43, 36,

 29, 22, 15, 23, 30, 37, 44, 51,

 58, 59, 52, 45, 38, 31, 39, 46,

 53, 60, 61, 54, 47, 55, 62, 63,

 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */

 63, 63, 63, 63, 63, 63, 63, 63

};





/*

 * Arithmetic utilities

 */



GLOBAL long

jdiv_round_up (long a, long b)

/* Compute a/b rounded up to next integer, ie, ceil(a/b) */

/* Assumes a >= 0, b > 0 */

{

  return (a + b - 1L) / b;

}





GLOBAL long

jround_up (long a, long b)

/* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */

/* Assumes a >= 0, b > 0 */

{

  a += b - 1L;

  return a - (a % b);

}





/* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays

 * and coefficient-block arrays.  This won't work on 80x86 because the arrays

 * are FAR and we're assuming a small-pointer memory model.  However, some

 * DOS compilers provide far-pointer versions of memcpy() and memset() even

 * in the small-model libraries.  These will be used if USE_FMEM is defined.

 * Otherwise, the routines below do it the hard way.  (The performance cost

 * is not all that great, because these routines aren't very heavily used.)

 */



#ifndef NEED_FAR_POINTERS	/* normal case, same as regular macros */

#define FMEMCOPY(dest,src,size)	MEMCOPY(dest,src,size)

#define FMEMZERO(target,size)	MEMZERO(target,size)

#else				/* 80x86 case, define if we can */

#ifdef USE_FMEM

#define FMEMCOPY(dest,src,size)	_fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))

#define FMEMZERO(target,size)	_fmemset((void FAR *)(target), 0, (size_t)(size))

#endif

#endif





GLOBAL void

jcopy_sample_rows (JSAMPARRAY input_array, int source_row,

		   JSAMPARRAY output_array, int dest_row,

		   int num_rows, JDIMENSION num_cols)

/* Copy some rows of samples from one place to another.

 * num_rows rows are copied from input_array[source_row++]

 * to output_array[dest_row++]; these areas may overlap for duplication.

 * The source and destination arrays must be at least as wide as num_cols.

 */

{

  register JSAMPROW inptr, outptr;

#ifdef FMEMCOPY

  register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE));

#else

  register JDIMENSION count;

#endif

  register int row;



  input_array += source_row;

  output_array += dest_row;



  for (row = num_rows; row > 0; row--) {

    inptr = *input_array++;

    outptr = *output_array++;

#ifdef FMEMCOPY

    FMEMCOPY(outptr, inptr, count);

#else

    for (count = num_cols; count > 0; count--)

      *outptr++ = *inptr++;	/* needn't bother with GETJSAMPLE() here */

#endif

  }

}





GLOBAL void

jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,

		 JDIMENSION num_blocks)

/* Copy a row of coefficient blocks from one place to another. */

{

#ifdef FMEMCOPY

  FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));

#else

  register JCOEFPTR inptr, outptr;

  register long count;



  inptr = (JCOEFPTR) input_row;

  outptr = (JCOEFPTR) output_row;

  for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) {

    *outptr++ = *inptr++;

  }

#endif

}





GLOBAL void

jzero_far (void FAR * target, size_t bytestozero)

/* Zero out a chunk of FAR memory. */

/* This might be sample-array data, block-array data, or alloc_large data. */

{

#ifdef FMEMZERO

  FMEMZERO(target, bytestozero);

#else

  register char FAR * ptr = (char FAR *) target;

  register size_t count;



  for (count = bytestozero; count > 0; count--) {

    *ptr++ = 0;

  }

#endif

}

